All athletes worry about maximizing their performance in a career that, for many, can be heartbreakingly short.

But only a handful fret about whether they have what it takes to be the most marketable in the land.

What are the keys to entrancing corporate America? Keith Lambrecht, director of sport management programs at Loyola University Chicago, sees three crucial aspects.

"They must be the best in their game in a large-enough market, they need a good personality, and they must be a good citizen, which will become more important as the issue of performance-enhancing drugs takes the forefront across all sports," Lambrecht said.

Here are eight U.S. athletes poised to score big in endorsements in 2008:

1. Tiger WoodsWoods, whose annual endorsement income is estimated to top $100 million thanks to Nike, Buick and other successful suitors, will maintain his leading role as the top pitchman in all sports. He is becoming more appealing as he ages — the fact that he's a family man with baby Sam Alexis has humanized this once-robotic superstar. The chance that the U.S. will recover the Ryder Cup on home soil in Louisville — and that Woods may, for once, play to his potential in that tournament — is an added bonus for those looking to sign him.

2. LeBron James
James has become the must-see player in the NBA, and his poise and business acumen off the court (he even runs his own marketing company) is attractive to many firms. Expect the U.S. star to break out big in China — where a LeBron Nike sneaker was recently introduced — during the Summer Olympics, leading to international endorsement offers. Already estimated by Fortune to bring about $25 million a year from endorsements, his one drawback is playing in small-market Cleveland (and on a Cavalier team that flails without him). Yet at 23, barring injuries, he has the most marketing potential of anyone in the NBA over the next 15 years.

3. Tom Brady
Brady is in position to achieve the biggest on-field success imaginable: the first NFL perfect season in the 16-game era. A fourth Super Bowl ring and an historic 19-0 mark would send Brady's marketability soaring, past even the man who has dominated endorsements for NFL players for years, Peyton Manning. New England’s Brady, who plays in a bigger market than Manning, is part of a team that has captured America's imagination, and his good looks and humble manner appeal to consumers.

4. Peyton Manning
Manning is still the king among NFL endorsers. His commercials for MasterCard and others dominate NFL telecasts, but there is not a lot of upside left for the veteran quarterback. Capturing the Super Bowl last year boosted his marketability, but he's been playing for a decade and will likely finish his career in small-market Indianapolis without any additional titles (at least as long as Bill Belichick coaches the Patriots). Unlike some superstars, though, his appeal will follow him into retirement.

5. Dale Earnhardt Jr.
Barely in his 30s, the son of legendary NASCAR driver Dale Earnhardt Sr., is already a veteran of ads played during the Super Bowl, the commercial extravaganza of the year. Back in 2004, he told USA Today he made more in endorsements (estimated at $5 million then) than driving. That is truer than ever now, especially since his race team inked an estimated $25 million deal last year with the National Guard and Amp energy drink. Companies know that linking their products to stars of NASCAR, with their passionate fans, guarantees a sales boost, and no one can jumpstart sales like Earnhardt.

6. Alex Rodriguez
With 80-plus names — many still active — seeing their endorsement value plummet with the release of the Mitchell Report, Rodriguez sits in an enviable spot. Untainted by steroid accusations, he plays in the nation's biggest market and on baseball's most storied franchise, the New York Yankees. He survived the bird-brained strategy of upstaging the World Series with a free agency announcement and will now finish his career with the Yankees, possessing a good chance of breaking Barry Bonds' home-run record. Rodriguez's endorsements may be pocket change compared to his MLB-record salary, but with the high cost of living in NYC, he won't be complaining.

7. Dwyane Wade
Teammate Shaquille O’Neal’s endorsement value is fading, but Wade’s is getting stronger. He recently signed with the William Morris Agency, which will work to snag endorsements for Wade around the Olympics this summer, when the charismatic guard will represent the U.S. team in Beijing. He plays in a big market and boasts dazzling on-court moves. If Miami can win the title — as it did in 2006 — Wade will enjoy more endorsement pitches.

8. David Beckham
This may be the biggest wild card of 2008. He brought priceless publicity to himself and to Major League Soccer last year with his move to America, but his endorsement appeal going forward will really depend upon his play, which was inconsistent last season because of injury. If he can't make the headlines and highlight shows with jaw-dropping moves and assists and take the Los Angeles Galaxy to the title game, one of the world's best-known soccer players — who's aging quickly — may find the American endorsement market weak indeed.

Last, but not least …
No matter whether Ohio State or LSU captures the national championship Jan. 7, their respective conferences — the Big 10 and the SEC — have already won big.

The maximum number of Big 10 teams and SEC teams possible (two per conference) has filled four of the 10 BCS bowl slots (Illinois and Georgia are the others). Both conferences will receive $21.5 million from those games ($17 million for the conference champion, $4.5 million for the other entrants). In addition, the biggest payout in a non-BCS Bowl — $4.25 million per team for the Jan. 1 Capital One Bowl — featured the Big Ten’s Michigan against Florida of the SEC.

Don’t feel too badly for the Big 12, which gets $21.5 million thanks to Oklahoma and Kansas’ appearances in BCS bowls, and another $3 million for Missouri’s Cotton Bowl visit. Of course, expenses to play in any of these games (lodging, travel, salaries and the like) can top $1 million per team, so it’s not pure profit.